It's important to keep in mind that you should not use a domain name or subdomain that you plan to host content with as the hostname of your server. Instead, set your hostname to a subdomain that you do not plan to use for hosting content. EX:

Code:

server123.server.com

Then, remove any previous DNS entries for the subdomain. This will allow you to create it as it's own account through Web Host Manager. At that point, you can upload files through FTP or File Manager.